answers of geophysics parts
CDP: the reflecting point which is common for a subset of data
CMP: having the same midpoint between source and receiver
Ghost: (1)energy that travel upward from an energy release and then is reflected downward. such that occurs at the weathering or at the surface. Ghost energy usually joins the traveling wave train to change the effective wave shape. (2)energy reflected from water surface before being picked up by a submerged receiver
Migration: an inversion operation involving rearrangement of
seismic information elements so that reflections and diffractions are plotted on their locations
Mud: an aqueous suspension used in rotary drilling. Mud is pumped down through the drill pipe and up through an annular space between the wall and the hole
Mud log: as a rotary well is drilled samples of the circulating mud and its suspended drill cutting are examined for lothology and hydrocarbons by visual observation and for gas phase constituents by a Whealstone bridge "hot-wire" partition gas chromatograph or hydrogen flame ionization analyzer. a mud log is a plot of such measurements together with a lithologic log and drilling time log.
- a log made with a micro log sonde with the arms collapsed so that the measuring pad is not pressed against the borehole wall. Measure the resistivity of mud at in hole conditions
Multiple: seismic energy that has been reflected more than once
Muting: in the early part of a record long offset traces may be muted (excluded from the stack ) because they are dominated by reflection arrivals.
NMO: the difference in reflection arrival time because the geophone is not located at source point. Usually applied to common midpoint gathers, it is the additional travel time required because of offset, assuming that the reflecting bed is not dipping and the ray paths are straight. This leads to hyperbolic
Shape for a reflection
Pull up : an apparent uplift caused by local shallower high velocity region. Opposite to pull down which results from low velocity layer.
Stacking: combining traces from different records to produse one trace
Time lag: the amount by which arrival times are larger than expected. Indicates that some of the paths from source to detector include a low speed portion
How to measure interval velocity?
The velocity of an interval in the subsurface is measured by determining the travel time over a depth interval along some ray path
How to measure reflection coefficient ?
The ratio between amplitude of reflected wave to that of incident wave. The relationship is obtained by solving boundary condition equations which express the continuity of displacement and stress at the boundary
The normal incidence reflection coefficient at an interface that separates two media of density ρ1, ρ2 and velocities V1, V2
(R c=(p2v2-p1v1)/(p2v2+p1v1
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